A not too uncommon problem with cellular phone service is that calls are dropped during a conversation between the calling and called parties. Prior art systems exist, such as Avaya's Digital HotDesk system, (described in the attached Appendix and incorporated herein by reference), that will attempt to reconnect dropped calls for calls that are being controlled by the subscriber's telephony server where this server provides a find-me/follow me feature. With such find me/follow me systems, a call placed to a subscriber's normal phone number is routed to an auxiliary number. That is, by way of example, a call placed to called subscriber's office phone is rerouted to his cell-phone. With the prior art reconnect system, the outbound call (between the server and the called party's cell phone) is monitored in an attempt to identify the occurrence of a cellular cut-off, that is, the loss of the call connection due to network coverage limitations. Typically, this is done by waiting a specified period of time, after the called party has cleared down, while the calling party is still holding onto the call. If the time period is exceeded, the system will automatically place a call back to the called party, and provide a voice message to the calling party (e.g., “Please remain on the line while we attempt to reconnect your call”). If the called party's cellular phone is available and he answers the call, then the calling party and called party are reconnected. Typically such a system will try to reconnect to the called party for a given time period, and if unsuccessful during this period it will then place the calling party into the called party mailbox.
Such a reconnect system, when working properly, has various advantages to both the called and calling parties. From the calling party's prospective, they do not have to redial in the event of a call being lost due to limitations in cellular coverage—they will either be reconnected to the called party or they will be offered a chance to leave a message. The called party knows that the call will be reestablished and waits for this to happen. If it is not, he can later check for a message. If used correctly, such a system eliminates the possible reaction of both parties trying to place a call to each other simultaneously and unavoidably missing each other due to call collision or limited call appearances on their telephony devices.
These prior art reconnect systems suffer from a serious deficiency in that the identification of a cellular cut-off is not always done properly. Such false alarms cause reconnection for calls intended to be terminated. Moreover, such systems encounter problems when a mobile subscriber is involved with a conference call.
The present invention overcomes these problems in the prior art by being able to more accurately determine whether or not a cellular cut-off has occurred. It also permits the reconnect feature to be implemented even when the called party joins a conference call.